Trace metal uptake and accumulation pathways in Kemp's ridley sea turtles (Lepidochelys kempii)

Abstract

Little is known of trace metal concentrations and their possible role in the\nmortality of critically endangered Kemp??s ridley sea turtles (Lepidochelys kempii).\nResearch described herein characterized concentrations of seven trace metals ??\nAg, Cd, Cr, Cu, Hg, Pb and Zn ?? in the blood and carapace tissue of captive\nKemp??s ridleys for use in assessing levels of these metals in wild counterparts.\nConcentrations of same trace metals were characterized in post-pelagic through\nadult life stages of 127 wild Kemp??s ridleys captured from the Gulf of Mexico and\nsoutheast Atlantic during 2000 to 2002. Blood, carapace, liver, kidney, and\nmuscle tissues from live and/or stranded Kemp??s ridleys were analyzed for the\naforementioned trace metals via graphite furnace atomic absorption\nspectrophotometer and cold vapor atomic fluorescence techniques conducted\nunder class-100 clean laboratory conditions. Similar trace metal assessments\nwere conducted on blue crab (Callinectes sapidus) prey to determine the role of\nfood as a possible uptake pathway in Kemp??s ridleys. \n\tOverall, trace metal levels in live, captive as well as wild ridleys were higher\nin carapace tissue than in blood. Carapace concentrations of Ag, Cr and Hg in\nKemp??s ridleys across all post-pelagic life stages increased with increasing\nstraight carapace length (SCL). Carapace tissue of wild ridleys exhibited higher\nCr, Hg, and Pb levels than their blue crab prey, regardless of study area;\nwhereas, crabs yielded higher Ag and Cu concentrations. Dead stranded ridleys\nyielded higher Ag, Cr, Hg, Pb, Zn levels in carapace tissue, whereas, their liver\nexhibited higher Cd and Cu levels. This finding suggests carapace tissue could\nserve as a suitable surrogate sample source for internal organs/tissues when\nmonitoring exposure of live Kemp??s ridleys to certain metals. The fact that larger,\nstranded ridleys exhibited higher Ag, Cd, Hg, Pb and Zn levels than did their\nsmaller, live analogs from Texas and Louisiana implies that these older ridleys\nhad increased opportunities to accumulate higher metal concentrations in their\ncarapace tissue than did their younger conspecifics. This trend suggests that\ncarapace tissue has the potential to accumulate trace metals while blood-borne\nconcentrations reflect only recent exposure to trace metals.